Farming the Sea

Interesting piece at National Geographic about future fish farms. The latest notion is to build big, robot-controlled fish cages that could roam the oceans under their own very minimal power, letting the fish be kept clean by currents and largely fed by whatever comes in through the mesh of the cage. This makes some sense.

I have a question about aquaculture. There are big areas of the ocean where there isn't much life of any kind, especially in the central Pacific. And the reason there isn't much life is that there aren't sufficient minerals in the water, especially iron, for the algae that start the food chain. What I wonder is, why can't find some way to disperse iron and other minerals into the water in these locations, starting our own food chains?

Everybody knows that some parts of the ocean are much more productive than others, again, largely because of the mineral content of the water. Why can't we change that?

I really don't know if this is feasible or not.